Tag: Spinal cord herniation

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Ventral Spinal Cord Displacement: A Guide to Differentiating Spinal Cord Herniation From Dorsal Arachnoid Web

Operative Neurosurgery 30:977–984, 2026

This article reviews imaging and operative distinctions between spinal arachnoid webs (SAW) and spinal cord herniation (SCH), using two detailed case illustrations with narrated 2-D operative videos. It highlights diagnostic imaging features, intraoperative findings, and tailored surgical techniques to optimize differentiation and management.

Focusing on technical nuance, the paper contrasts midline-sparing unilateral laminectomy and arachnoid lysis for SAW with bilateral laminectomy, cord mobilization, and ventral alloderm sling reconstruction for SCH, and emphasizes intraoperative ultrasound and neuromonitoring for safe reduction and decompression.

Problem: Spinal arachnoid web (SAW) and spinal cord herniation (SCH) can present similarly (myelopathy/radiculopathy) and both often look like focal anterior cord displacement on MRI, yet require very different operative strategies.

Definitions: SAW is abnormally thickened arachnoid tissue in the subarachnoid space that can tether/compress the cord and disrupt CSF flow (edema/syrinx), while SCH is cord displacement through an opening in the dura/arachnoid (often ventral).

Imaging workup: CT myelography is recommended to evaluate/confirm suspected findings because its resolution can outperform MRI for distinguishing these entities.

Key imaging clues: Visible ventral CSF between cord and ventral dura argues against herniation, while absence of ventral CSF supports SCH; cord twisting at the abnormal level is a more specific sign for SCH; the “scalpel sign” is commonly linked to SAW but can occur in both.

Limits of imaging: Arachnoid webs are below MRI/CT resolution, and diagnostic patterns are imperfect (reported SAWs can lack the scalpel sign or mimic SCH on CT myelogram).

SAW surgery: Definitive treatment is lysis/excision of the thickened arachnoid band, often via laminectomy with ultrasound localization; dentate ligament division can help inspect the ventral compartment to exclude ventral pathology.

SCH surgery: Management typically uses wider exposure (often bilateral laminectomy), spinal cord mobilization/rotation (sectioning dentate ligaments ± dorsal rootlets), reduction of the herniation, and placement/suturing of a ventral alloderm sling to span the dural defect, with close neuromonitoring and ultrasound confirmation.

Outcomes in cases: SAW case showed postoperative normalization of cord position and complete syrinx regression after web excision/lysis; SCH case showed complete reduction of herniation on postoperative MRI with substantial functional improvement (including near-resolution of bowel/bladder symptoms).

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A New Classification for Pathologies of Spinal Meninges, Part 1: Dural Cysts, Dissections, and Ectasias

Neurosurgery 81:29–44, 2017

The clinical significance of pathologies of the spinal dura is often unclear and their management controversial.

OBJECTIVE: To classify spinal dural pathologies analogous to vascular aneurysms, present their symptoms and surgical results.

METHODS: Among 1519 patients with spinal space-occupying lesions, 66 patients demonstrated dural pathologies. Neuroradiological and surgical features were reviewed and clinical data analyzed.

RESULTS: Saccular dural diverticula (type I, n = 28) caused by defects of both dural layers, dissections between dural layers (type II, n = 29) due to defects of the inner layer, and dural ectasias (type III, n = 9) related to structural changes of the dura were distinguished. For all types, symptoms consisted of local pain followed by signs of radiculopathy or myelopathy, while one patient with dural ectasia presented a low-pressure syndrome and 10 patients with dural dissections additional spinal cord herniation. Type I and type II pathologies required occlusion of their dural defects via extradural (type I) or intradural (type II) approaches. For type III pathologies of the dural sac no surgerywas recommended. Favorable results were obtained in all 14 patients with type I and 13 of 15 patients with type II pathologies undergoing surgery.

CONCLUSION: The majority of dural pathologies involving root sleeves remain asymptomatic, while those of the dural sac commonly lead to pain and neurological symptoms. Type I and type II pathologies were treated with good long-term results occluding their dural defects, while ectasias of the dural sac (type III) were managed conservatively.

 

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